DESCRIPTION: This application from proposes to standardize measurements of differentiation-, proliferation-, and cell cycle-phase related and regulatory antigens in growing cells, as a means of extending the utility of the DNA content measurements now used for clinical and research purposes to characterize growing cell populations. The differentiation related markers, used to identify different histologic subpopulations, include intermediate filaments, and the proliferation markers include PCNA. Cyclins D, E, and B1 and P105 will be examined as cell cycle-related antigens, and products of genes such as myc, ras, and neu will be studied as regulatory proteins. Standardization will be accomplished by both biochemical analysis and by use of secondary standards in the form of fluorescent or antibody-binding beads. Additional studies will be carried out in collaboration with the University of Rochester and Los Alamos National Laboratory to determine whether the addition, respectively, of morphologic information derived from slit-scanning or of fluorescence lifetime information determined using a phase-sensitive (in this case referring to the phase of light waves, not cell cycle phase) flow cytometer improves detection sensitivity.